1. The word that differs in the position of primary stress:
- A. stomach (primary stress on the first syllable)
- B. expert (primary stress on the first syllable)
- C. prefer (primary stress on the second syllable)
- D. knowledge (primary stress on the first syllable)

The answer is C. prefer.

2. The word that differs in the position of primary stress:
- A. benefit (primary stress on the first syllable)
- B. confident (primary stress on the first syllable)
- C. charity (primary stress on the first syllable)
- D. important (primary stress on the second syllable)

The answer is D. important.